Intracranial aspiration catheter

ABSTRACT

Disclosed is an access catheter, having a distal segment which is movable from a reduced outside diameter for positioning at a target site, and an enlarged outside diameter to create an enlarged internal working lumen. In one application, the catheter is configured for use as an intracranial aspiration catheter. Methods are also disclosed.

This application is a divisional of U.S. patent application Ser. No.10/623,875 filed Jul. 21, 2003 which claims priority under 35 U.S.C.§119 to U.S. Provisional Patent Application Ser. No. 60/398,071, filedJul. 23, 2002, the disclosure of which is incorporated in its entiretyherein by reference.

BACKGROUND OF THE INVENTION

Stroke is the third most common cause of death in the United States andthe most disabling neurologic disorder. Approximately 700,000 patientssuffer from stroke annually. Stroke is a syndrome characterized by theacute onset of a neurological deficit that persists for at least 24hours, reflecting focal involvement of the central nervous system, andis the result of a disturbance of the cerebral circulation. Itsincidence increases with age. Risk factors for stroke include systolicor diastolic hypertension, hypercholesterolemia, cigarette smoking,heavy alcohol consumption, and oral contraceptive use.

Hemorrhagic stroke accounts for 20% of the annual stroke population.Hemorrhagic stroke often occurs due to rupture of an aneurysm orarteriovenous malformation bleeding into the brain tissue, resulting incerebral infarction. The remaining 80% of the stroke population areischemic strokes and are caused by occluded vessels that deprive thebrain of oxygen-carrying blood. Ischemic strokes are often caused byemboli or pieces of thrombotic tissue that have dislodged from otherbody sites or from the cerebral vessels themselves to occlude in thenarrow cerebral arteries more distally. When a patient presents withneurological symptoms and signs which resolve completely within 1 hour,the term transient ischemic attack (TIA) is used. Etiologically, TIA andstroke share the same pathophysiologic mechanisms and thus represent acontinuum based on persistence of symptoms and extent of ischemicinsult.

Emboli occasionally form around the valves of the heart or in the leftatrial appendage during periods of irregular heart rhythm and then aredislodged and follow the blood flow into the distal regions of the body.Those emboli can pass to the brain and cause an embolic stroke. As willbe discussed below, many such occlusions occur in the middle cerebralartery (MCA), although such is not the only site where emboli come torest.

When a patient presents with neurological deficit, a diagnostichypothesis for the cause of stroke can be generated based on thepatient's history, a review of stroke risk factors, and a neurologicexamination. If an ischemic event is suspected, a clinician cantentatively assess whether the patient has a cardiogenic source ofemboli, large artery extracranial or intracranial disease, small arteryintraparenchymal disease, or a hematologic or other systemic disorder. Ahead CT scan is often performed to determine whether the patient hassuffered an ischemic or hemorrhagic insult. Blood would be present onthe CT scan in subarachnoid hemorrhage, intraparenchymal hematoma, orintraventricular hemorrhage.

Traditionally, emergent management of acute ischemic stroke consistedmainly of general supportive care, e.g. hydration, monitoringneurological status, blood pressure control, and/or anti-platelet oranti-coagulation therapy. In 1996, the Food and Drug Administrationapproved the use of Genentech Inc.'s thrombolytic drug, tissueplasminogen activator (t-PA) or Activase®, for treating acute stroke. Arandomized, double-blind trial, the National Institute of NeurologicalDisorders and t-PA Stroke Study, revealed a statistically significantimprovement in stoke scale scores at 24 hours in the group of patientsreceiving intravenous t-PA within 3 hours of the onset of an ischemicstroke. Since the approval of t-PA, an emergency room physician could,for the first time, offer a stroke patient an effective treatmentbesides supportive care.

However, treatment with systemic t-PA is associated with increased riskof intracerebral hemorrhage and other hemorrhagic complications.Patients treated with t-PA were more likely to sustain a symptomaticintracerebral hemorrhage during the first 36 hours of treatment. Thefrequency of symptomatic hemorrhage increases when t-PA is administeredbeyond 3 hours from the onset of a stroke. Besides the time constraintin using t-PA in acute ischemic stroke, other contraindications includethe following: if the patient has had a previous stroke or serious headtrauma in the preceding 3 months, if the patient has a systolic bloodpressure above 185 mm Hg or diastolic blood pressure above 110 mmHg, ifthe patient requires aggressive treatment to reduce the blood pressureto the specified limits, if the patient is taking anticoagulants or hasa propensity to hemorrhage, and/or if the patient has had a recentinvasive surgical procedure. Therefore, only a small percentage ofselected stroke patients are qualified to receive t-PA.

Obstructive emboli have also been mechanically removed from varioussites in the vasculature for years. For example, the “Fogarty catheter”or variations thereof has been used, typically in the periphery, toremove clots from arteries found in legs and in arms. These well knowndevices are described, for example, in U.S. Pat. No. 3,435,826, toFogarty and in U.S. Pat. Nos. 4,403,612 and 3,367,101. In general, thesepatents describe a balloon catheter in which a balloon material islongitudinally stretched when deflated.

In procedures for removing emboli using the Fogarty catheter or othersimilar catheters, it is typical, first, to locate the clot usingfluoroscopy. The embolectomy catheter is then inserted and directed tothe clot. The distal tip of the balloon catheter is then carefully movedthrough the center of the clot. Once the balloon has passed through thedistal side of the clot, the balloon is inflated. The balloon catheteris then gradually proximally withdrawn. The balloon, in this way, actsto pull the clot proximally ahead of the balloon to a point where it canbe retrieved. The majority of procedures using a Fogarty type catheterrepeat these steps until the pertinent vessel is cleared of clotmaterial.

A variety of alternative emboli retrieval catheters have also beendeveloped, in which various wire corkscrews and baskets must be advanceddistally through the embolic material in order to achieve capture andremoval. However, removal of emboli using such catheters carriesattendant potential problems. One such problem occurs when advancing thecatheter through the clot dislodges material to a more remote site whereremoval may become more difficult or impossible.

New devices and methods are thus needed in treating vasculatureocclusions in the body, including patients with acute ischemic strokeand occlusive cerebrovascular disease, in treating symptomatic patientswith embolization or hemodynamic compromise, or in stroke prevention,e.g., patients with incidental finding of asymptomatic carotid lesion,which improve a patient's neurological function and quality of lifewithout causing significant side effect, and can thus also be used inpatients with contraindication to the use of t-PA.

SUMMARY OF THE INVENTION

There is provided in accordance with one aspect of the presentinvention, a method for removing thromboembolic material from a carotidor cerebral artery. The method comprises the steps of providing acatheter having a proximal end, a distal end, an expandable distalsection having a distal port, an aspiration lumen communicating with theport, and an axially movable support. The distal end of the catheter isinserted into the artery, and the support is distally advanced to expandthe distal section. Negative pressure is applied to the aspiration port,to draw the thromboembolic material into the distal section.

The carotid artery may be the common carotid artery, the internalcarotid artery or the carotid siphon. Alternatively, the artery may bethe middle cerebral artery or the anterior cerebral artery, or elsewherein the brain.

The method may additionally comprise the steps of introducing oxygenatedmedium into the artery through the aspiration lumen, or infusingpharmaceutical agent into the artery through the aspiration lumen. Thepharmaceutical agent may be a vasodilator such as nifedipine ornitroprusside. The pharmaceutical agent may alternatively comprise t-PA.The thromboembolic material may be located using intravascularultrasound, or carotid doppler.

In accordance with another aspect of the present invention, there isprovided an intracranial aspiration catheter. The catheter comprises anelongate flexible tubular body, having a proximal end, a distal end, andan aspiration lumen extending therethrough. The aspiration lumen in adistal section of the body is movable between a first, reduced insidediameter for transluminal navigation and a second, enlarged insidediameter for aspirating material. A support is provided, forcontrollably supporting the aspiration lumen against collapse when inthe second diameter. A control is provided on the proximal end of thecatheter for controlling the support. In one implementation, the supportcomprises a spiral element such as a spring coil. The support may beaxially movable, such as between a proximal position when the distalsection is in the low cross sectional configuration, and a distalposition in which the distal section is enlarged, and supported againstcollapse under aspiration. Alternatively, the support is activated byrotating a first end of the support relative to a second end of thesupport.

The aspiration lumen may be defined within a tubular wall having aplurality of folds therein, when the aspiration lumen is in the firstinside diameter configuration. Alternatively, the aspiration lumen maybe defined within a wall made from a stretchable material.

In accordance with another aspect of the present invention, there isprovided a method of establishing a flow path through a catheter,positioned across a non-linear segment of vasculature. The methodcomprises the steps of transluminally navigating an enlargeable tubularwall through a non-linear segment of vasculature, and manipulating asupport within a tubular wall to enlarge the inside diameter of thetubular wall to create a flow path across the non-linear segment. Themanipulating step may comprise distally advancing a tubular supportstructure within the tubular wall. In one implementation, the methodcomprises distally advancing a coil within the tubular wall.

In accordance with a further aspect of the present invention, there isprovided a method of aspirating material. The method comprises the stepsof transluminally advancing a catheter to the site of an obstruction,the catheter having an aspiration lumen therein. A support is movedwithin the aspiration lumen, and, thereafter, material is aspirated fromthe obstruction through the aspiration lumen.

In accordance with another aspect of the present invention, there isprovided an intracranial aspiration catheter. The catheter comprises anelongate flexible tubular body, having a proximal end, a distal end, andan aspiration lumen extending therethrough. The distal section on thebody is movable between a first, reduced inside diameter fortransluminal navigation, and a second, enlarged inside diameter foraspirating material. A support is axially movable between a proximalposition when the aspiration lumen is in the first diameter, and adistal position for supporting the aspiration lumen against collapsewhen in the second diameter.

In one implementation, the support comprises a coil. The distal sectionmay have a length of no greater than about 20 cm, in certain embodimentsa length of no greater than about 10 cm, and often within the range offrom about 5 cm to about 15 cm.

Further features and advantages of the present invention will becomeapparent to those of skill in the art in view of the detaileddescription of preferred embodiments which follows, when consideredtogether with the attached drawings and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side elevational schematic view of an intracranialaspiration catheter in accordance with the present invention, with adistal segment in a reduced crossing profile configuration.

FIG. 2 is a side elevational view as in FIG. 1, with the distal segmentin an enlarged cross-sectional configuration.

FIG. 3A is a cross-sectional view taken along the line 3-3 in FIG. 1.

FIG. 3B is an alternate cross-section through an intracranial aspirationcatheter having an over-the-wire configuration.

FIG. 4A is a cross-sectional view taken along the line 4-4,schematically showing a folding pattern for the distal section.

FIG. 4B is a cross-sectional view as in FIG. 4A, showing an alternatefolding pattern.

FIG. 5 is a side elevational cross-sectional view through a distalportion of the catheter of FIG. 1, illustrating an axially movablesupport coil in a proximal position.

FIG. 6 is a cross-sectional view as in FIG. 5, with the axially movablesupport coil in a distal position.

FIG. 7 is a cross-sectional view as in FIG. 5, showing an alternatesupport coil in a proximal position.

FIG. 8 is a cross-sectional view as in FIG. 7, with the alternatesupport coil in a distal position.

FIG. 9 is a schematic representation of the reversed circulation in thecircle of Willis, to compensate for an occlusion in the left carotidsiphon artery, with a guidewire extending through the left internalcarotid artery to the occlusion.

FIG. 10 is a schematic illustration as in FIG. 9, with an intracranialaspiration catheter advanced to the occlusion, in the reduced diameterconfiguration.

FIG. 11 is a schematic representation as in FIG. 10, with the distalsection of the catheter in the enlarged diameter configuration.

FIG. 12 is a schematic representation as in FIG. 11, followingaspiration of the occlusion through the enlarged diameter of theaspiration catheter.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIG. 1, there is disclosed a catheter 10 in accordance withone aspect of the present invention. Although primarily described in thecontext of a an expandable distal segment aspiration catheter with asingle central lumen, catheters of the present invention can readily bemodified to incorporate additional structures, such as permanent orremovable column strength enhancing mandrels, two or more lumen such asto permit drug or irrigant infusion or radiation delivery or to supplyinflation media to an inflatable balloon, or combinations of thesefeatures, as will be readily apparent to one of skill in the art in viewof the disclosure herein. In addition, the present invention will bedescribed primarily in the context of removing obstructive material fromremote vasculature in the brain.

The catheters disclosed herein may readily be adapted for use throughoutthe body wherever it may be desirable to introduce a low profilecatheter and then provided a relatively large diameter aspiration orsupported working channel. For example, low diameter catheter shafts inaccordance with the present invention may be dimensioned for usethroughout the coronary and peripheral vasculature, the gastrointestinaltract, the urethra, ureters, Fallopian tubes and other lumens andpotential lumens, as well. The expandable lumen structure of the presentinvention may also be used as a minimally invasive percutaneous tissuetract expander, such as for diagnostic or therapeutic access to a solidtissue target (e.g., breast biopsy or tissue excision).

The catheter 10 generally comprises an elongate tubular body 16extending between a proximal end 12 and a distal functional end 14. Thelength of the tubular body 16 depends upon the desired application. Forexample, lengths in the area of from about 120 cm to about 140 cm ormore are typical for use in femoral access percutaneous transluminalcoronary applications. Intracranial or other applications may call for adifferent catheter shaft length depending upon the vascular access site,as will be understood in the art.

In the illustrated embodiment, the tubular body 16 is divided into atleast a fixed diameter proximal section 33 and an adjustable diameterdistal section 34 separated by a transition 32, discussed infra.Alternatively, the adjustable diameter feature of distal section 34 canextend the entire length of the catheter from the manifold 18 or otherproximal connector to distal tip 25, as will become apparent from thedisclosure herein.

The proximal end 12 of catheter 10 is additionally provided with amanifold 18 having one or more access ports as is known in the art.Generally, manifold 18 is provided with a guidewire port 20 in anover-the-wire construction, and an aspiration port 22. Alternatively,the aspiration port 22 may be omitted if the procedure involves removalof the guidewire proximally from the guidewire port 20 followingplacement of the aspiration catheter, and aspiration through theguidewire port. Additional access ports may be provided as needed,depending upon the functional capabilities of the catheter. Manifold 18may be injection molded from any of a variety of medical grade plastics,or formed in accordance with other techniques known in the art.

Manifold 18 is additionally provided with a control 24, for controllingthe radial expansion of the distal segment 34 of the catheter. Control24 may take any of a variety of forms depending upon the mechanicalstructure of the support. In the illustrated embodiment, control 24comprises a slider switch which is mechanically axially movably linkedto the distal support (discussed below) such that proximal retraction ofthe slider switch 24 produces a proximal movement of the support. Thisallows the unsupported distal section 34 to assume its low profileconfiguration as illustrated in FIG. 1. Distal axial advancement of theslider switch 24 produces a distal axial advance of the support, asillustrated in FIG. 2. In the distal position, the support advances thedistal segment 34 from the reduced diameter as illustrated in FIG. 1, tothe enlarged diameter as illustrated in FIG. 2. In the enlargedconfiguration, the support maintains patency of a central lumenextending through the distal segment 34 to accommodate aspiration aswill be discussed below.

Any of a variety of controls may be utilized, including switches,levers, rotatable knobs, pull/push wires, and others which will beapparent to those of skill in the art in view of the disclosure herein.

Referring to FIG. 3A, there is illustrated a cross-sectional viewthrough the proximal section 33 of the catheter shaft 16 of theembodiment of FIG. 1. In the illustrated embodiment, the proximalsection 33 comprises a two lumen extrusion, having a control wire lumen30 with an axially movable control wire 32 therein, and an aspirationlumen 38. Aspiration lumen 38 also can serve as the guidewire lumen.Alternatively, the proximal section 33 can be formed having a concentricconfiguration if desired.

In an alternate configuration, as illustrated in FIG. 3B, a three lumenextrusion is utilized in the proximal section 33. A separate guidewirelumen 28 is provided, for allowing an over-the-wire configuration inwhich the guidewire does not need to be removed in order to accomplishaspiration. The guidewire lumen 28 therefore extends between a proximalaccess port 20 on the manifold 18, and a distal internal access port(not illustrated) at which point the guidewire lumen 28 opens distallyinto the aspiration lumen 38. Generally, the distal access port will bespaced substantially distally from the manifold along the length of thecatheter. The distal access port may be positioned anywhere within therange of from about 10 cm to about 60 cm from the distal end of thecatheter. This enables a partial proximal withdrawal of the guidewirefollowing placement of the catheter, to allow use of the aspirationlumen 38 as will be apparent to those of skill in the art. However, theguidewire may remain within the guidewire lumen 28, such that it can bereadily distally advanced into the distal vasculature, such as forrepositioning or replacement of the catheter 10.

The distal section 34 comprises a thin flexible wall defining a centrallumen 38 extending axially therethrough. The flexible wall is capable ofmoving between a reduced crossing profile configuration, such as thatillustrated in FIG. 1, and an enlarged crossing profile configurationsuch as that illustrated in FIG. 2. The reduced crossing profileconfiguration of FIG. 1 is provided for transluminal navigation ofdistal torturous vasculature to reach a target site. Once the targetsite has been reached, the distal segment 34 is radially enlarged andsupported to provide an enlarged working channel such as an aspirationlumen as will be discussed below.

Movement of the distal section 34 from the reduced diameter to theenlarged diameter may be accomplished in a variety of ways, dependingupon the desired construction. Referring to FIG. 4A, for example, a thinwalled tubular segment is provided having an enlarged diameter, such asequivalent to the enlarged diameter of FIG. 2. The tubular segment isfolded such as by partially collapsing a first wing 42 and a second wing44, leaving a reduced diameter central lumen 38 having a sufficientinside diameter to axially advance over a guidewire. The first andsecond wings 42 and 44 are thereafter wrapped around a central portion46 of the distal section 34 as illustrated in FIG. 4A. The resultingfolded configuration may be retained by applying a heat set as is knownin the balloon angioplasty arts. The distal section 34 may be attachedin the vicinity of transition 32 using well known catheter fabricationtechniques.

In general, the collapsed diameter of lumen 38 will be approximately0.003 inches or greater larger than the outside diameter of the intendedguidewire. Guidewires having diameters in the range of from about 0.009inches to about 0.016 inches are presently contemplated.

Avoiding a tight fit between the guidewire 40 and inside diameter ofguidewire lumen 28 enhances the slideability of the catheter over theguidewire. In ultra small diameter catheter designs, it may be desirableto coat the outside surface of the guidewire 40 and/or the insidesurface of the wall defining lumen 38 with a lubricous coating tominimize friction as the catheter 10 is axially moved with respect tothe guidewire 40. A variety of coatings may be utilized, such asParalene, Teflon, silicone rubber, polyimide-polytetrafluoroethylenecomposite materials or others known in the art and suitable dependingupon the material of the guidewire or inner tubular wall 38.

In an alternate configuration, as illustrated in FIG. 4B, the tubularwall 40 is provided with a plurality of wings 46. Each of these may befolded and provided with a heat set to produce a reduced diameterconfiguration. Alternatively, the tubular wall 40 may be extruded in thewinged configuration, depending upon the desired manufacturingtechnique.

Referring to FIGS. 5 and 6, a movable support 50 is provided forenlarging the distal section 34 from the reduced diameter to theenlarged diameter configuration. In the illustrated embodiment, themovable support 50 is in the form of an axially movable coil 52. Coil 52is mechanically linked to the control 24 by an axially movable controlwire 32. Distal advance of the control 24 causes the control wire 32 toadvance distally through the control wire lumen 30, thereby advancingthe movable coil 52 from a position within the proximal section 33,across the transition 32 and into the distal section 38. This causes thedistal section 38 to move from the reduced diameter to the enlargeddiameter configuration.

The coil 52 resists collapse of the tubular wall 40 when vacuum isapplied to the central lumen 38. Due to the radial supportcharacteristics of the movable coil 52, the wall thickness of thetubular wall 40 may be minimized to a limit which is determined byphysical characteristics of the polymer, together with the spacingbetween adjacent filars of the movable coil 52. Optimal relationshipsbetween these variables can be determined through routineexperimentation by those of ordinary skill in the art, in view of thedisclosure herein.

The use of an axially movable coil 52 is believed to enable both radialenlargement of the distal aspiration lumen 38, as well as placement of alarge ID aspiration lumen in small vessels, even around corners in thevasculature. The catheter can be placed within torturous vasculaturewhile in the low profile configuration, to reach a remote site. Distaladvance of the support coil within the catheter can then track throughthe tortuous vasculature while radially enlarging the aspiration lumen.This is enabled through the use of a laterally flexible tubular support,such as a helix, spring, micro slotted tube or other tubular supportwith lateral flexibility. In this manner, the distal section 34 may bepositioned within portions of the anatomy and then enlarged to adiameter which would not have been able to axially traverse thevasculature without unacceptable levels of vascular trauma, usingconventional catheter constructions.

The exact configuration of the movable support 50 may be variedconsiderably, and still accomplish the objectives of the presentinvention. For example, referring to FIGS. 7 and 8, the movable support50 is in the form of a helical ribbon 54. The helical ribbon 54 may beprovided by helically cutting through the wall of a segment of thedistal end of a tube 56 using techniques which are disclosed elsewhereherein. Thus, as illustrated in FIG. 8, a support zone 58 is provided onthe distal end of a tube 56. Tube 56 may extend concentrically withinthe central lumen 38 proximally to the manifold 18, or to a control onthe proximal catheter shaft. Alternatively, 256 may be in mechanicalcommunication with the control 24 by way of an axially movable controlwire 32 as has been discussed. Ribbon 54 may alternatively be formed bywrapping around a mandrel, or other techniques which will be known tothose of skill in the art.

Aspiration catheters of the present invention which are adapted forintracranial applications generally have a total length in the range offrom 60 cm to 250 cm, usually from about 135 cm to about 175 cm. Thelength of the proximal segment 33 will typically be from 20 cm to 220cm, more typically from 100 cm to about 120 cm. The length of the distalsegment 34 will typically be in the range from 2 cm to about 50 cm,usually from about 5 cm to about 20 cm. The proximal and distal bodysegments 33, 34 may be joined to each other, i.e. at a transition 32.The body segments may be joined in any of a variety of conventionalmanners, such as heat fusion, adhesive bonding, coextrusion, or thelike. In the exemplary embodiment, the two body segments 33, 34 will beformed separately and thereafter fused together by the application ofheat with a removable mandrel extending through each lumen which crossesthe transition 32 to maintain patency. An outer shrink wrap tubing maybe used to add structural integrity by spanning the transition 32.

The catheters of the present invention may be composed of any of avariety of biologically compatible polymeric resins having suitablecharacteristics when formed into the tubular catheter body segments.Exemplary materials include polyvinyl chloride, polyethers, polyamides,polyethylenes, polyurethanes, copolymers thereof, and the like. Incertain embodiments, in which the distal segment 34 dilates (stretches)radially rather than unfolds, the distal segment 34 may be formed frommore elastic materials, such as latex rubber, silicone rubber, andblends thereof. In one embodiment, both the proximal body segment 33 anddistal body segment 34 will comprise a polyvinyl chloride (PVC), withthe proximal body segment being formed from a relatively rigid PVC andthe distal body segment being formed from a relatively flexible, supplePVC. Optionally, the proximal body segment may be reinforced with ametal or polymeric braid or other conventional reinforcing layer.

The proximal body segment will exhibit sufficient column strength topermit axial positioning of the catheter through a guide catheter atleast a portion of with the distal body segment 34 extending into thepatient's vasculature. The proximal body segment may have a shorehardness in the range from 50 D to 100 D, often being about 70 D to 80D. Usually, the proximal shaft will have a flexural modulus from 20,000psi to 1,000,000 psi, preferably from 100,000 psi to 600,000 psi. Thedistal body segment will be sufficiently flexible and supple so that itmay navigate the patient's distal vasculature. In highly flexibleembodiments, the shore hardness of the distal body segment 34 may be inthe range of from about 20 A to about 100 A, and the flexural modulusfor the distal segment 34 may be from about 50 psi to about 15,000 psi.

The catheter body may further comprise other components, such asradiopaque fillers; colorants; reinforcing materials; reinforcementlayers, such as braids and helical reinforcement elements; or the like.In particular, the proximal body segment may be reinforced in order toenhance its column strength and torqueability while preferably limitingits wall thickness and outside diameter.

The pleated or otherwise reduced diameter of the distal body segment 34will usually be smaller than that of the proximal body segment. In someintracranial applications, the proximal body segment will have aconstant diameter, with an outer diameter in the range from 0.33 mm to 2mm, usually from 0.67 mm to 1.67 mm, and an inner diameter in the rangefrom 0.1 mm to 1.75 mm, usually from 0.2 mm to 1 mm. The distal bodysegment can be tapered, where its proximal end has a diameter whichgenerally is the same as that of the distal end of the proximal bodysegment and its distal end has a diameter no greater than the range setforth above.

Usually, radiopaque markers will be provided at least at the distal end25 and the transition region 32 between the proximal and distal bodysegments 33, 34. Other radiopaque markers may be provided elsewhere,such as on the support coil, if it is not already radiopaque. Oneradiopaque marker comprises a metal band which is fully recessed withinthe distal end of the proximal body segment 33. Suitable marker bandscan be produced from a variety of materials, including platinum, gold,and tungsten/rhenium alloy. Preferably, the radiopaque metal band willbe recessed in an annular channel formed at the distal end of theproximal body segment.

The proximal section 33 of tubular body 16 may be produced in accordancewith any of a variety of known techniques for manufacturinginterventional catheter bodies, such as by extrusion of appropriatebiocompatible polymeric materials. Alternatively, at least a proximalportion or all of the length of tubular body 16 may comprise a polymericor metal spring coil, solid walled hypodermic needle tubing, or braidedreinforced wall, as is known in the microcatheter arts.

In many applications, the proximal section 33 of tubular body 16 isprovided with an approximately circular cross-sectional configurationhaving an external diameter within the range of from about 0.025 inchesto about 0.065 inches. In accordance with one embodiment of theinvention, the proximal section 33 of tubular body 16 has an externaldiameter of about 0.042 inches (3.2 f) throughout most of its length.Alternatively, a generally oval or triangular cross-sectionalconfiguration can also be used, as well as other noncircularconfigurations, depending upon the method of manufacture, number andarrangement of internal lumens and the intended use.

In a catheter intended for peripheral vascular applications, theproximal section 33 of body 16 will typically have an outside diameterwithin the range of from about 0.039 inches to about 0.065 inches. Incoronary vascular applications, the proximal section 33 of body 16 willtypically have an outside diameter within the range of from about 0.025inches to about 0.045 inches. The illustrated construction of distalsection 34 permits lower external cross-sections in the collapsedconfiguration, as low as 0.028 inches or 0.025 inches or 0.022 inches orlower as may be desired for remote coronary or intracranialapplications.

Diameters outside of the preferred ranges may also be used, providedthat the functional consequences of the diameter are acceptable for theintended purpose of the catheter. For example, the lower limit of thediameter for any portion of tubular body 16 in a given application willbe a function of the number of fluid or other functional lumen containedin the catheter, together with the acceptable minimum aspiration flowrate and collapse resistance.

Tubular body 16 must have sufficient structural integrity (e.g., columnstrength or “pushability”) to permit the catheter to be advanced todistal locations without buckling or undesirable bending of the tubularbody. The ability of the body 16 to transmit torque may also bedesirable, such as to avoid kinking upon rotation, to assist insteering. The tubular body 16, and particularly the distal section 34,may be provided with any of a variety of torque and/or column strengthenhancing structures. For example, axially extending stiffening wires,spiral wrapped support layers, braided or woven reinforcement filamentsmay be built into or layered on the tubular body 16. See, for example,U.S. Pat. No. 5,891,114 to Chien, et al., the disclosure of which isincorporated in its entirety herein by reference.

In many applications, the proximal section 33 will not be required totraverse particularly low profile or tortuous arteries. For coronaryvascular applications, for example, the proximal section 33 will bemostly or entirely within the relatively large diameter guide catheter.The transition 32 can be located on the catheter shaft 16 to correspondapproximately with the distal end of the guide catheter when the balloon24 and/or distal end 14 is at the treatment site. Viewed the other way,the length of the distal section 34 is preferably at least as long asthe distance from the ostium of the relevant coronary artery to thetreatment site. In most applications, the transition 32 will be at leastabout 3 cm, preferably at least about 5 cm and alternatively as much asabout 10 cm but often not more than about 20 cm from the distal end ofthe catheter. Distances as much as 30 cm to 50 cm or greater between thetransition 32 and distal end of the catheter may also be desirable insome applications.

For certain other applications, such as intracranial catheterizations,the distal section 34 is preferably at least about 5 cm long and smallenough in diameter to pass through vessels as low as 3 mm or 2 mm orlower. Catheters for this application may have a proximal section lengthof between about 60 cm to about 150 cm and a distal section length ofbetween about 5 cm to about 15 cm, and the distal section is able totrack a tortuous path of at least about 5 cm through vessels of lessthan about 3 mm lumen ID. Further structure, dimensional and methoddisclosure can be found in U.S. Pat. No. 4,739,768 to Engelson, thedisclosure of which is incorporated in its entirety herein by reference.

The distal section 34, may be manufactured as an extrusion. In onemethod of manufacture, the extrusion is formed from a medium to highmelt index polyethylene or other polymer having an outside diameter ofgreater than the diameter of the desired finished product. The rawextrusion can thereafter be drawn down to the desired diameter, inaccordance with known processing techniques. The draw down pull speedcan be varied such as along a proximal portion of the extrusion toproduce a taper to a larger proximal diameter. This permits a smoothtransition 32 from the relatively smaller outside diameter distalsection 34 to the typically larger outside diameter of proximal section33. High melt index materials allow the production of a greater numberof different diameter draw downs by adjusting pull speed and otherprocess parameters, for a given set of tooling as will be appreciated bythose of skill in the art. The distal end 14 can be further reduced indiameter by an additional draw down step if desired.

Referring to FIGS. 7 and 8, the axially movable support may be providedin the form of an elongate flexible tube 56. A distal section 58 oftubular element 56 is provided with a spiral cut, to retain radialstrength but provide lateral flexibility. The spiral cut section 58generally has a length within the range of from about 1 centimeter to 15centimeters, preferably within a range of about 5 centimeters to about12 centimeters, and, in a particular embodiment, extends forapproximately 10 centimeters in length. The spiral cut generally has apitch within the range of from about 0.01 inches to about 0.125 inches,and in one embodiment, has a 0.06 pitch. In another embodiment, thedistal section 32 comprises a first spiral cut section having a lengthof about 5 cm and a pitch of about 0.06, and a second, distal sectionhaving a length of about 5 cm and a pitch of about 0.030.

Preferably, the spiral cut extends completely through the wall of thetubular element 56 to produce a helical or coiled configuration. Theprecise pitch of the spiral cut and axial spacing of adjacent windingscan be varied widely while still accomplishing the purposes of thepresent invention, and can be optimized for any particular applicationin view of the disclosure herein.

For example, polytetrafluoroethylene tubing, such as that suitable fortubular element 30, can be commercially obtained from Zeus, inOrangeburg, S.C. The distal section 32 can be provided with a spiralcut, such as by any of a variety of techniques that can be devised bythose of skill in the art. In accordance with one technique, the PTFE orother tubing is placed onto a mandrel. The mandrel is attached to amachine with a predetermined screw thread. A cutting element such as arazor blade or other sharp instrument is placed across the tubing andthe machine is activated to rotate the mandrel. As rotation of themachine (screw thread) occurs, the mandrel moves axially androtationally causing the tubing to be cut in a spiral manner by thecutting implement. The machine can be set up to cut either a right orleft hand spiral. The machine can also be set to cut continuous orvariable pitch spirals, or multizone spiral sections in which each zonehas a unique pitch. A metal spring coil 34 can be wrapped about asuitably sized rotating mandrel as is known in the art, with the distalopen wound section 36 formed by stretching.

The tubular support 58 may alternatively be in the form of a wirespring, extending throughout the length of the distal segment or entirecatheter. See Generally FIGS. 5 and 6. A distal section 36 of the coilspring 52 is stretched axially to produce an open wound configuration,such that the axial space between adjacent windings of the coil may bewithin the range of from about 0.05 mm to about 1 mm or greater. Theproximal portion of coil spring 34 is generally bottomed out (notillustrated), such that adjacent windings of the coil are in contactwith one another. This provides column strength, to allow distaladvancement within the catheter, while retaining lateral flexibility.Alternatively, the coil spring can be open wound with, e.g., 0.01 mm to1 mm spacing for the entire length.

A variety of materials can be used to construct the coil spring 52, suchas stainless steel, platinum, platinum alloy, nickel, or titaniumalloys. Coil spring 52 can be produced from any of a variety of stockforms, such as round cross-sectional wire, square or other rectangularwire, or polymeric materials as are known in the art. In one embodiment,coil spring 52 is wound from a flat wire made from stainless steel andhaving cross-sectional dimensions of about 0.002 by about 0.006 inches.

The cerebral circulation is regulated in such a way that a constanttotal cerebral blood flow (CBF) is generally maintained under varyingconditions. For example, a reduction in flow to one part of the brain,such as in acute stroke, may be compensated by an increase in flow toanother part, so that CBF to any one region of the brain remainsunchanged. More importantly, when one part of the brain becomes ischemicdue to a vascular occlusion, the brain compensates by increasing bloodflow to the ischemic area through its collateral circulation.

FIG. 9 depicts a normal cerebral circulation and formation of Circle ofWillis. Aorta 100 gives rise to right brachiocephalic trunk 82, leftcommon carotid artery (CCA) 80, and left subclavian artery 84. Thebrachiocephalic artery further branches into right common carotid artery85 and right subclavian artery 83. The left CCA gives rise to leftinternal carotid artery (ICA) 90 which becomes left middle cerebralartery (MCA) 97 and left anterior cerebral artery (ACA) 99. Anteriorly,the Circle of Willis is formed by the internal carotid arteries, theanterior cerebral arteries, and anterior communicating artery 91 whichconnects the two ACAs. The right and left ICA also send right posteriorcommunicating artery 72 and left posterior communicating artery 95 toconnect, respectively, with right posterior cerebral artery (PCA) 74 andleft PCA 94. The two posterior communicating arteries and PCAs, and theorigin of the posterior cerebral artery from basilar artery 92 completethe circle posteriorly.

When an occlusion occurs acutely, for example, in left carotid siphon70, as depicted in FIG. 9, blood flow in the right cerebral arteries,left external carotid artery 78, right vertebral artery 76 and leftvertebral artery 77 increases, resulting in directional change of flowthrough the Circle of Willis to compensate for the sudden decrease ofblood flow in the left carotid siphon. Specifically, blood flow reversesin right posterior communicating artery 72, right PCA 74, left posteriorcommunicating artery 95. Anterior communicating artery 91 opens,reversing flow in left ACA 99, and flow increases in the left externalcarotid artery, reversing flow along left ophthalmic artery 75, all ofwhich contribute to flow in left ICA 90 distal the occlusion to provideperfusion to the ischemic area distal to the occlusion. A guidewire isillustrated in position proximal to the occlusion.

In use, the distal end of the aspiration catheter 10 is inserted throughan incision on a peripheral artery over the guidewire into a more distalcarotid or intracranial artery, such as the terminal ICA, carotidsiphon, MCA, or ACA. Thromboembolic material 202 is shown occluding thelumen of a cerebral artery narrowed by atheromatous plaque 200. Theocclusion site can be localized with cerebral angiogram or IVUS. Inemergency situations, the catheter can be inserted directly into thesymptomatic carotid artery after localization of the occlusion with theassistance of IVUS or standard carotid doppler and TCD.

As illustrated in FIG. 10, the catheter 10 is transluminally navigatedalong or over the guidewire, to a position just proximal to theocclusion. Transluminal navigation is accomplished with the distalsection of the catheter in the first, reduced cross sectionalconfiguration. This enables navigation of tortuous vasculature which alarger cross section may not be able to traverse.

Referring to FIG. 11, the cross section of the distal segment isenlarged after the catheter has been positioned, such as by distallyaxially advancing a tubular support as has been described previously.This allows a larger inside diameter aspiration lumen than wouldotherwise have been navigable to the treatment site. In addition, theuse of a coil or spiral wrapping as the tubular support enables thedistal segment to be expanded through curves in the vasculature, withoutkinking or straightening the vasculature. As will be appreciated fromeven the simplified schematic of the cerebral vasculature shown in FIG.11, the length of the distal section may be varied depending upon theintended target site for the catheter. Since the inside diameter of thevasculature decreases distally, the length and collapsed crossingprofile of the distal section is designed to take into account thelength and inside diameter of the vessel leading up to a targetocclusion.

Aspiration is thereafter applied to the aspiration lumen, therebydrawing the occlusion into the catheter as illustrated in FIG. 12. Thedistal section may thereafter be reduced in cross section, and thecatheter proximally retracted from the patient. A vasodilator, e.g.,nifedipine or nitroprusside, may be injected through lumen 38 and port25 to reverse vascular spasm induced as a result of instrumentation.

Pressure may be monitored by a manometer and can be altered by applyingvacuum to the proximal end of the catheter. A pressure dial, which maybe included in the proximal end of the catheter, allows suction withinthe vessel to be regulated. When continuous negative pressure isapplied, occluding material 202 is dislodged into aspiration port 25 andproximally through aspiration lumen 38.

If the occlusion is not removed by the above continuous suction method,intermittent suction can be used to create an alternatingnegative-positive pressure gradient, which may dislodge thethromboembolic occlusion. Alternatively, a thrombolytic agent, e.g.,t-PA may be infused through lumen 38 and port 25 to lyse the occlusionif soft thrombus is suspected. Standard atherectomy or angioplasty withor without stent placement can also be performed on atheromatous plaqueafter removal of the occlusion if perfusion through the diseased arteryis still inadequate.

Focal hypothermia, which has been shown to be neuroprotective, can beadministered by perfusing hypothermic oxygenated blood or fluid.Perfusion through port 25 can be achieved by withdrawing venous bloodfrom a peripheral vein and processing through a pump oxygenator, or bywithdrawing oxygenated blood from a peripheral artery, such as a femoralartery, and pumping it back into the carotid artery.

If suction fails to dislodge the occlusion, a thrombolytic agent, e.g.,t-PA, can be infused through lumen 38 and port 25 to lyse any thromboticmaterial with greater local efficacy and fewer systemic complications.Administration of thrombolytic agent, however, may not be recommendedfor devices which are inserted directly into the carotid artery due toincreased risk of hemorrhage. If perfusion is continued for more than afew minutes, removal of excess fluid from the circulation is required toavoid fluid overload. Fluid can be withdrawn from a jugular vein or fromany other peripheral vein or artery, e.g., the femoral vein or artery,and re-introduced into the symptomatic artery. Moderate hypothermia, atapproximately 32 to 34° C., can be introduced during the fluidrecirculation.

In patients with vertebral artery occlusions, treatment with angioplastyoften results in disastrous complications due to embolization of theocclusive lesion downstream to the basilar artery. Emboli small enoughto pass through the vertebral arteries into the larger basilar arteryare usually arrested at the top of the basilar artery, where itbifurcates into the posterior cerebral arteries. The resulting reductionin blood flow to the ascending reticular formation of the midbrain andthalamus produces immediate loss of consciousness. The devices describedin FIG. 1 through FIG. 8 can be used to remove thromboembolic materialfrom the vertebral artery. The occlusion site is first localized withtranscranial doppler and angiogram. The catheter 10 can be insertedthrough an incision on a peripheral artery into the symptomaticvertebral artery or the subclavian artery. For example, the distal endof catheter 10 may be inserted proximal to thromboembolic material 202in right vertebral artery 87 and left subclavian artery 84. Whencontinuous or intermittent suction is applied to the distal end of thecatheter, the pressure gradient across the occluding lesion increasesand thromboembolic material 202 may be dislodged and captured by theaspiration port. The thromboembolic material may thereafter be removedcontinuous or pulsed suction, thereby reducing the risk of embolizationto the basilar artery.

Access for the catheter of the present invention can be achieved usingconventional techniques through an incision on a peripheral artery, suchas right femoral artery, left femoral artery, right radial artery, leftradial artery, right brachial artery, left brachial artery, rightaxillary artery, left axillary artery, right subclavian artery, or leftsubclavian artery. An incision can also be made on right carotid arteryor left carotid artery 130 in emergency situations.

The length of the catheter for those access sites to reach the brainwill generally be between 20 to 100 centimeters, preferablyapproximately between 30 and 60 centimeters. The inner diameter of thecatheter may be between 0.2 and 0.6 centimeters, or smaller. Theforegoing ranges are set forth solely for the purpose of illustratingtypical device dimensions. The actual dimensions of a device constructedaccording to the principles of the present invention may obviously varyoutside of the listed ranges without departing from those basicprinciples.

Although the present invention has been described in terms of certainpreferred embodiments, it may be incorporated into other embodiments bypersons of skill in the art in view of the disclosure herein. The scopeof the invention is therefore not intended to be limited by the specificembodiments disclosed herein, but is intended to be defined by the fullscope of the following claims.

1. A method for removing thromboembolic material from a carotid orcerebral artery, comprising the steps of: providing a catheter having aproximal end, a distal end, an expandable distal section having a distalport, an aspiration lumen communicating with the port, and an axiallymovable support; inserting the distal end of the catheter into theartery; distally axially advancing the support to expand the distalsection; and applying a negative pressure to the aspiration port, todraw the thromboembolic material into the distal section.
 2. The methodof claim 1, wherein the carotid artery is the common carotid artery. 3.The method of claim 1, wherein the carotid artery is selected from thegroup consisting of the internal carotid artery and carotid siphon. 4.The method of claim 1, wherein the artery is the middle cerebral artery.5. The method of claim 1, wherein the artery is the anterior cerebralartery.
 6. The method of claim 1, further comprising the step ofintroducing oxygenated medium into the artery through the aspirationlumen.
 7. The method of claim 6, wherein the oxygenated medium ishypothermic.
 8. The method of claim 1, further comprising the step ofinfusing pharmaceutical agent into the carotid artery through theaspiration lumen.
 9. The method of claim 8, wherein the pharmaceuticalagent is a vasodilator.
 10. The method of claim 9, wherein thevasodilator is selected from the group consisting of nifedipine andnitroprusside.
 11. The method of claim 8, wherein the pharmaceuticalagent is t-PA.
 12. The method of claim 1, further comprising the step oflocalizing the thromboembolic material with intravascular ultrasound.13. The method of claim 1, further comprising the step of localizing thethromboembolic material with carotid doppler.
 14. A method ofestablishing a flow path through a catheter, positioned across anonlinear segment of vasculature, comprising the steps of:transluminally navigating an enlargeable tubular wall through anonlinear segment of vasculature; manipulating a support within thetubular wall to enlarge the inside diameter of the tubular wall tocreate a flow path across the nonlinear segment.
 15. A method ofestablishing a flow path as in claim 14, wherein the manipulating stepcomprises distally advancing a tubular support structure within thetubular wall.
 16. A method of establishing a flow path as in claim 15,comprising distally advancing a coil within the tubular wall.
 17. Amethod of aspirating material, comprising the steps of: transluminallyadvancing a catheter to the site of an obstruction, the catheter havingan aspiration lumen therein; moving a support within the aspirationlumen; and thereafter aspirating material from the obstruction throughthe aspiration lumen.
 18. A method of aspirating material as in claim17, wherein the moving a support comprises distally advancing a tubularsupport.
 19. A method of aspirating material as in claim 18, wherein themoving a support comprises distally advancing a coil.
 20. A method ofaspirating material as in claim 17, wherein the obstruction is in thecommon carotid artery.
 21. A method of aspirating material as in claim17, wherein the obstruction is in the internal carotid artery.
 22. Amethod of aspirating material as in claim 17, wherein the obstruction isin the carotid siphon.
 23. A method of aspirating material as in claim17, wherein the obstruction is in the middle cerebral artery.
 24. Amethod of aspirating material as in claim 17, wherein the obstruction isin the anterior cerebral artery.
 25. An intracranial aspirationcatheter, comprising: an elongate, flexible tubular body, having aproximal end, a distal end, and an aspiration lumen extendingtherethrough; a distal section on the body in which the aspiration lumenis movable between a first, reduced inside diameter for transluminalnavigation and a second, enlarged inside diameter for aspiratingmaterial; a support which is axially movable between a proximal positionwhen the aspiration lumen is in the first diameter and a distal positionfor supporting the aspiration lumen against collapse when in the seconddiameter.
 26. An intracranial aspiration catheter as in claim 25,wherein the support comprises a coil.
 27. An intracranial aspirationcatheter as in claim 25, wherein the distal section has a length of nogreater than about 20 cm.
 28. An intracranial aspiration catheter as inclaim 25, wherein the distal section has a length of no greater thanabout 10 cm.
 29. An intracranial aspiration catheter as in claim 25,wherein the distal section has a length within the range of from about 5cm and about 15 cm.